This book discusses light, its properties as an electromagnetic wave, interaction with matter, and laser as an optical device. The first part discussions include qualitative arguments such as pictorial representations of the wave dynamics and analogy to other oscillatory systems to facilitate an intuitive understanding of the topics. The second part reviews light-matter interaction. It introduces the light-matter interaction while introducing the particular behavior of light, known as the photon, reviewing various properties of light waves resulting from the interaction with matters including the propagation of light in media. The last two sections focus on the fundamentals of lasers and the practical uses of lasers, including several techniques to control the spatial and temporal characteristics of laser beams. This book discusses acoustic waves' characteristics so that we can deepen our understanding of acoustic waves.